Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts.
Scientists at the Beltsville Agricultural Research Center and Univ. of Sao Paulo discuss epidemiology of T. gondii in Amazon, Brazil. The results will be of interest to veterinarian, parasitologists and public health workers.

Technical Abstract:
: Antibodies to Toxoplasma gondii were assayed in sera of 63 cats and 80 pigs from 71 farms located at Rondônia State, Western Amazon, Brazil by the modified agglutination test (MAT) and the indirect immunofluorescent antibody test (IFAT). Antibodies (MAT '1:25) were found in 55 of 63 cats (87.3%) with titers of 1:25 in 2, 1:50 in 2, 1:100 in 7, 1:200 in 1, 1:400 in 2, 1:800 in 9, 1:1,600 in 6 and 1:3,200 or higher in 26. By IFAT, antibodies were found in 55 cats (87.3%) with titers of 1:25 in 2, 1:50 in 1, 1:100 in 4, 1:200 in 4, 1:400 in 1, 1:800 in 13, 1:1,600 in 12 and 1:3,200 or higher in 18. In pig sera, by MAT, antibodies were found in 30 of 80 pigs (37.5 %) with titers of 1:25 in 2, 1:50 in 3, 1:100 in 2, 1:200 in 8, 1:400 in 3, 1:800 in 5, 1:1,600 in 3, and 1:3,200 or higher in 4. By using the IFAT (titers 1:64), antibodies were found in 35 (43.7%) pigs. The high seroprevalence of T. gondii in cats from the Amazon is indicative of high contamination of the environment by oocysts because these cats probably already shed oocysts. The ingestion of undercooked tissues of infected pigs can be a source of T. gondii infection for humans and cats.